Dosage units in the form of tablets are prepared by compressing a formulation containing a medicinal substance or drug and other ingredients, such as excipients selected for properties which enhance the production and use of the tablet. There are currently three known basic methods for preparing tablet granulations. These are wet granulation, dry granulation and direct compression. Both wet and dry granulations involve the formation of an agglomerate for feeding to a die cavity. Direct compression usually involves compressing a powder blend of an active ingredient with suitable excipients.
Other methods of preparing feedstock for preparing compression dosage units have been disclosed in the above-referenced copending applications as well as in copending, commonly owned U.S. application Ser. No. 08/194,682 filed Feb. 10, 1994. Each of these applications are incorporated herein by reference.
U.S. application Ser. No. 08/194,682 discloses a method of making a solid comestible by compressing shearform matrix masses sufficiently to form a comestible compression unit. U.S. application Ser. No. 08/259,496 discloses a method of preparing a quick dissolve low density comestible unit by mixing uncured shearform matrix and an additive, molding a unit dosage form therefrom, and curing the shearform matrix. Finally, U.S. application Ser. No. 08/259,258 discloses a method of preparing quick dissolve comestible units by initiating crystallization of shearform matrix, and combining, either before or after initiating crystallization, an additive with the shearform matrix to form flowable, compactible micro-particulates. Finally, the micro-particulate medium is compacted to form the quick dissolve comestible unit. In each of these disclosures, the tableting medium is prepared initially by use of shearform matrix. In most cases a quick dissolve tablet can be produced by providing a compressed body which is of low density and capable of being disintegrated and dispersed relatively rapidly, and in many cases, instantaneously.
Tableting processes known today in the art generally include the use of a machine which includes opposed upper and lower punches and die cavities positioned between the punches into which a tableting medium can be directed and subjected to compression between the punches. See, for example, U.S. Pat. No. 4,943,227; U.S. Pat. No. 4,880,373; U.S. Pat. No. 2,214,505 and U.S. Pat. No. 2,068,619. Other references which disclose different shapes of dosage units are U.S. Pat. No. 4,493,822, U.S. Pat. No. 4,376,111, and an excerpt from The Consumer Guide for "Prescription Drugs," p. 194-208, Publications International, Ltd. (1990).
The tablets which are formed in the die cavities must be transferred from the die to a package for ultimate distribution and sale. Typically after formation of the tablet, the upper and/or lower punches are removed from the cavity. In the manufacture of low density tablets, the tablets are retained in the cavities for transference to a further manufacturing station where the tablets are ejected into a package. However upon removal of the upper and lower punches the tablet is no longer captively retained in a die cavity. Further, as the upper and lower punches form a tight fit within the die cavity in order to properly form the tablet therein, removal of the punches creates a vacuum which tends to pull the tablet out from the cavity, or skew the tablet in the cavity. Such movement of a low density tablet in the die cavity makes the smooth transfer to a package more difficult.
It is therefore desirable to provide a method and apparatus for enabling the formation of low density tablets in a die cavity and the retention of the tablets in proper position within the cavity after formation and during transference.